Structures that transform in size or shape have numerous uses. If one desires to have a portable shelter of some kind, it should package down to a compact bundle (tents being a prime example).
I have discovered a method for constructing reversibly expandable truss-structures that provides for an extremely wide variety of geometries. Trusses formed by this method will collapse and expand in a controlled, smooth and synchronized manner. Such structures require no complex joints. Connections are limited to simple pivots. A unique characteristic of one embodiment of the present invention is that it provides a three-dimensional folding truss whose overall shape and geometry is constant and unchanging during the entire folding process. Only its size changes between a compact bundle and an extended self-supporting structure.
There are times when, rather than desiring a portable shelter, one wishes to have a structure that remains fixed to a site, but that can open and close. An example is a retractable roof over a stadium, swimming pool, theater or pavilion.
An alternate embodiment of the present invention provides reversibly retractable structures that open up from the center outwards, but maintain an essentially fixed perimeter. The kind of motion exhibited by such structures may be described as an iris-type motion.
The structure is a truss consisting of links joined by simple pivots. Coverings may be provided in various ways, such as attaching shingled plates or a flexible membrane to the truss.
In addition to retractable roofs, numerous other uses exist for this embodiment of the invention. Novel window shades, toys and special irises for lighting are examples.